Custom Functions and Add-Ins

I have a question in regards to custom functions in a shared workbook for Excel 2000. I have created several .xla add-ins which contain functions to be used by users in my company. The functions work great but I have run into a problem with some spreadsheets stored on our companies network and shared among a few users. The problem arises because when each of the users open up the spreadsheet the function appears with the full path of the .xla of the last user who saved the worksheet. So for example, instead of the function saying '=getd()' it says ='C:\Documents and Settings\Application Data\Microsoft\Add Ins\getdat.xla!getd()'. Because the users are using different operating systems (Win 98 and Win 2000) their add-ins are stored in different locations. Therefore, the user cannot use the functions (recieve a #name error) and has to update the location of the .xla everytime they open the sheet after the other user on a different machine has saved the sheet.
The users themselves do not enter this path but it is automatically generated when the sheet is opened by the other user.
I've looked on the MS KB for an answer but can't find one. Any help would be much appreciated,
Iain Macfarlane